Fix blocking I/O to load netrc when creating requests

[bdraco]

What do these changes do?

Fixes blocking I/O in the event loop when netrc authentication is used. Previously, netrc_from_env() was called synchronously in ClientRequest.__init__(), which would block the entire event loop while reading ~/.netrc from disk.

Now netrc lookup happens asynchronously in ClientSession._request() using loop.run_in_executor() before creating the request. Added a quick check for the NETRC environment variable to avoid spawning executor jobs unnecessarily since they're expensive.

Are there changes in behavior for the user?

No user-facing changes. Netrc authentication still works exactly the same way - it just won't block the event loop anymore.

Is it a substantial burden for the maintainers to support this?

no

Related issue number

Fixes #10435

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES/ folder

  • name it <issue_or_pr_num>.<type>.rst (e.g. 588.bugfix.rst)

  • if you don't have an issue number, change it to the pull request
    number after creating the PR

    • .bugfix: A bug fix for something the maintainers deemed an
      improper undesired behavior that got corrected to match
      pre-agreed expectations.
    • .feature: A new behavior, public APIs. That sort of stuff.
    • .deprecation: A declaration of future API removals and breaking
      changes in behavior.
    • .breaking: When something public is removed in a breaking way.
      Could be deprecated in an earlier release.
    • .doc: Notable updates to the documentation structure or build
      process.
    • .packaging: Notes for downstreams about unobvious side effects
      and tooling. Changes in the test invocation considerations and
      runtime assumptions.
    • .contrib: Stuff that affects the contributor experience. e.g.
      Running tests, building the docs, setting up the development
      environment.
    • .misc: Changes that are hard to assign to any of the above
      categories.

  • Make sure to use full sentences with correct case and punctuation,
    for example:

    Fixed issue with non-ascii contents in doctest text files
    -- by :user:`contributor-gh-handle`.

    Use the past tense or the present tense a non-imperative mood,
    referring to what's changed compared to the last released version
    of this project.

[Copilot]

Pull Request Overview

This PR fixes blocking I/O in the event loop when netrc authentication is used by moving netrc file lookup from synchronous execution in ClientRequest.__init__() to asynchronous execution in ClientSession._request() using loop.run_in_executor().

• Moved netrc authentication lookup from ClientRequest.update_auth() to ClientSession._request()
• Added environment variable check to avoid unnecessary executor jobs when NETRC is not set
• Removed blocking I/O allowances from test configuration

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
aiohttp/client.py	Added async netrc auth lookup in _request() method and helper _get_netrc_auth()
aiohttp/client_reqrep.py	Removed synchronous netrc auth logic from update_auth() method
tests/test_client_session.py	Added comprehensive tests for netrc authentication scenarios
tests/test_client_functional.py	Added functional tests for netrc authentication behavior
tests/test_client_request.py	Removed test that relied on synchronous netrc lookup
tests/conftest.py	Removed blocking I/O allowances and added netrc test fixtures
CHANGES/11634.bugfix.rst	Added changelog entry for the fix
CHANGES/10435.bugfix.rst	Added reference to the main bugfix changelog

---

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.74%. Comparing base (d261f8a) to head (ecba61b).
⚠️ Report is 5 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #11634   +/-   ##
=======================================
  Coverage   98.74%   98.74%           
=======================================
  Files         127      127           
  Lines       43467    43529   +62     
  Branches     2327     2327           
=======================================
+ Hits        42922    42984   +62     
  Misses        389      389           
  Partials      156      156           

Flag	Coverage Δ
CI-GHA	98.63% <100.00%> (+<0.01%)	⬆️
OS-Linux	98.36% <100.00%> (+<0.01%)	⬆️
OS-Windows	96.69% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.58% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	97.15% <100.00%> (+<0.01%)	⬆️
Py-3.10.18	97.65% <100.00%> (+<0.01%)	⬆️
Py-3.11.13	97.85% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.35% <100.00%> (+<0.01%)	⬆️
Py-3.12.10	97.45% <100.00%> (+<0.01%)	⬆️
Py-3.12.11	97.95% <100.00%> (+<0.01%)	⬆️
Py-3.13.7	98.20% <100.00%> (-0.01%)	⬇️
Py-3.14.0	98.16% <100.00%> (+<0.01%)	⬆️
Py-3.14.0t	97.23% <100.00%> (+<0.01%)	⬆️
Py-pypy3.10.16-7.3.19	88.31% <100.00%> (-6.52%)	⬇️
VM-macos	97.58% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	98.36% <100.00%> (+<0.01%)	⬆️
VM-windows	96.69% <100.00%> (+<0.01%)	⬆️

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[patchback]

Backport to 3.13: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply cde03b9 on top of patchback/backports/3.13/cde03b98c647272cf12f6e36cce35b5dc252171d/pr-11634

Backporting merged PR #11634 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.13/cde03b98c647272cf12f6e36cce35b5dc252171d/pr-11634 upstream/3.13

4. Now, cherry-pick PR Fix blocking I/O to load netrc when creating requests #11634 contents into that branch:

   $ git cherry-pick -x cde03b98c647272cf12f6e36cce35b5dc252171d

   If it'll yell at you with something like fatal: Commit cde03b98c647272cf12f6e36cce35b5dc252171d is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x cde03b98c647272cf12f6e36cce35b5dc252171d

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix blocking I/O to load netrc when creating requests #11634 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.13/cde03b98c647272cf12f6e36cce35b5dc252171d/pr-11634

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to 3.14: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply cde03b9 on top of patchback/backports/3.14/cde03b98c647272cf12f6e36cce35b5dc252171d/pr-11634

Backporting merged PR #11634 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.14/cde03b98c647272cf12f6e36cce35b5dc252171d/pr-11634 upstream/3.14

4. Now, cherry-pick PR Fix blocking I/O to load netrc when creating requests #11634 contents into that branch:

   $ git cherry-pick -x cde03b98c647272cf12f6e36cce35b5dc252171d

   If it'll yell at you with something like fatal: Commit cde03b98c647272cf12f6e36cce35b5dc252171d is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x cde03b98c647272cf12f6e36cce35b5dc252171d

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix blocking I/O to load netrc when creating requests #11634 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.14/cde03b98c647272cf12f6e36cce35b5dc252171d/pr-11634

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[bdraco]

Let me see if I can do the back ports this morning. I've been a bit under water with ESPHome release items

[bdraco]

Bit of a hairy conflict